Tumor growth rate varies with age in lethargic mutant BALB/cGnDu mice

BALB/cGnDu lethargic mutant mice suffer from an age-related temporary defect in their cell-mediated immune response which is "spontaneously" corrected in animals 7 weeks of age or older. Thus, mutants of different ages (3 to 4 weeks old and 7 to 9 weeks old) were used to compare tumor incidence, tumor growth rate, and host survival time of Harding-Passey (HP) melanoma, mKSA, and GI110(BK)B6D2Tu tumors. Normal littermates were used as controls. Only the HP tumor was successfully transplanted in all recipients. In the 3- to 4-week-old lethargic mutants, the HP tumor had an increased growth rate and decreased the mean lifespan of the mice, when compared to normal littermates, but only one mKSA and no GI110(BI)B6D2Tu tumors proved transplantable. In contrast, lethargic mutants 7 to 9 weeks old injected with the HP tumor survived longer than their normal littermates, and they did not accept either of the other tumors tested. These results corroborate the notion that leghargic mutant mice have a partially impaired anti-tumor cell-mediated immune response at 3 to 4 weeks of age, but that their anti-tumor response is enhanced at the time of their "spontaneous" correction of the immune deficiency. The need for future studies on the possible use of this model to study various human immunological and adrenal disorders is discussed.